canvas.toDataURL() 安全错误

Question

So I'm using google maps and I get the picture so it looks like this

<img id="staticMap"
        src="http://maps.googleapis.com/maps/api/staticmap?center=Brooklyn+Bridge,New+York,NY&zoom=13&size=600x300&maptype=roadmap
&markers=color:blue%7Clabel:S%7C40.702147,-74.015794&markers=color:green%7Clabel:G%7C40.711614,-74.012318
&markers=color:red%7Ccolor:red%7Clabel:C%7C40.718217,-73.998284&sensor=false">

I need to save it. I have found this:

function getBase64FromImageUrl(URL) {
    var img = new Image();
    img.src = URL;
    img.onload = function() {

        var canvas = document.createElement("canvas");
        canvas.width = this.width;
        canvas.height = this.height;

        var ctx = canvas.getContext("2d");
        ctx.drawImage(this, 0, 0);

        var dataURL = canvas.toDataURL("image/png");

        alert(dataURL.replace(/^data:image\/(png|jpg);base64,/, ""));

    };
}

But I get this problem:

Uncaught SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': tainted canvases may not be exported.

I searched for fixes. I found a sample here How to use CORS but still I can't tie these 2 pieces of code together to make it work. Maybe I'm doing it the wrong way and there is a simpler way to do it? I'm trying to save this pic so that I can transfer the data to my server. So maybe someone did something like this and knows how to make .toDataURL() work as I need it?

Answer 1

Unless google serves this image with the correct Access-Control-Allow-Origin header, then you wont be able to use their image in canvas. This is due to not having CORS approval. You can read more about this here , but it essentially means:

Although you can use images without CORS approval in your canvas, doing so taints the canvas. Once a canvas has been tainted, you can no longer pull data back out of the canvas. For example, you can no longer use the canvas toBlob(), toDataURL(), or getImageData() methods; doing so will throw a security error.

This protects users from having private data exposed by using images to pull information from remote web sites without permission.

I suggest just passing the URL to your server-side language and using curl to download the image. Be careful to sanitise this though!

EDIT:

As this answer is still the accepted answer, you should check out @shadyshrif's answer , which is to use:

var img = new Image();
img.setAttribute('crossOrigin', 'anonymous');
img.src = url;

This will only work if you have the correct permissions, but will at least allow you to do what you want.

Answer 2

Just use the crossOrigin attribute and pass 'anonymous' as the second parameter

var img = new Image();
img.setAttribute('crossOrigin', 'anonymous');
img.src = url;

Answer 3

This method will prevent you from getting an 'Access-Control-Allow-Origin' error from the server you are accessing to.

var img = new Image();
var timestamp = new Date().getTime();
img.setAttribute('crossOrigin', 'anonymous');
img.src = url + '?' + timestamp;

Answer 4

Try the code below ...

<img crossOrigin="anonymous"
     id="imgpicture" 
     fall-back="images/penang realty,Apartment,house,condominium,terrace house,semi d,detached,
                bungalow,high end luxury properties,landed properties,gated guarded house.png" 
     ng-src="https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png" 
     height="220"
     width="200"
     class="watermark">

Answer 5

In my case I was using the WebBrowser control (forcing IE 11) and I could not get past the error. Switching to CefSharp which uses Chrome solved it for me.

Answer 6

I had the same error message. I had the file in a simple .html, when I passed the file to php in Apache it worked

html2canvas(document.querySelector('#toPrint')).then(canvas => {
            let pdf = new jsPDF('p', 'mm', 'a4');
            pdf.addImage(canvas.toDataURL('image/png'), 'PNG', 0, 0, 211, 298);
            pdf.save(filename);
        });

Answer 7

if the picture from the third site didn't set the head of cors,you can never download the picture file through the chrome, even if you use the setAttribute('crossOrigin', 'anonymous'); Here are some suggestions

1. hack the chrome
2. write a program to download the picture and then use it with file

Answer 8

By using fabric js we can solve this security error issue in IE.

    function getBase64FromImageUrl(URL) {
        var canvas  = new fabric.Canvas('c');
        var img = new Image();
        img.onload = function() {
            var canvas1 = document.createElement("canvas");
            canvas1.width = this.width;
            canvas1.height = this.height;
            var ctx = canvas.getContext('2d');
            ctx.drawImage(this, 0, 0);
            var dataURL = canvas.toDataURL({format: "png"});
        };
        img.src = URL;
    }